“Hired Guns” takes an in-depth look at how guns can be put into the hands of security guards in the U.S. who endanger public safety.

Special Investigative Reports Airs Tuesday, December 9 and Wednesday, December 10 during Anderson Cooper 360° at 8pm ET

A yearlong investigation by CNN and The Center for Investigative Reporting (CIR) found, despite the image of safety, armed security guards often themselves pose a threat to the public due to a combination of lax laws, minimal oversight and almost no accountability.

The joint investigation revealed that one can become an armed security guard in 15 states with no firearms training. Nine states don’t even run an FBI criminal background check. And in 27 states, you can be banned by federal law from carrying a gun and still become an armed guard. Only four states require armed guards to undergo psychological testing.

In part one of HIRED GUNS, airing Tuesday Dec 9, CNN’s Drew Griffin investigates the case of an armed guard with a history of alcohol abuse who is charged with murder in the shooting death outside a Miami nightclub. The guard claims he was defending himself when he shot two men at least 12 times. One of the men died and the other is paralyzed. Since being locked up, doctors have determined there is a “substantial likelihood” that the former security guard is suffering from a mental illness and he has been deemed incompetent to stand trial.

In part two, airing Wednesday December 10, the investigation focuses on poor government oversight nationwide. That is evident in an Arizona case where an armed security guard chased snack food shoplifters from a convenience store he was guarding and ended up shooting the driver of the getaway car. The security guard never should have been licensed to carry a gun as he was designated a “prohibited possessor” due to his criminal record as a juvenile. The investigation found that state officials never checked his juvenile record or a federal “prohibited possessor” database, and cleared him to be an armed guard.

Many in the industry want tougher standards and, at the minimum, federal background checks for all armed guards, but the CNN/CIR investigation found that most of the proposed legislation to mandate those checks has failed.

HIRED GUNS is the third collaboration between CNN and CIR. Last year’s CNN/CIR investigation “Rehab Racket” won the IRE Award and was a national Emmy nominee. Anderson Cooper 360° airs weeknights at 8pm ET on CNN.